Construction method of duplex heterostructure of reducer gear

Abstract

The application provides a kind of biphase heterogeneous structure construction method of speed reducer gear, comprising the following steps: according to the size specification of speed reducer gear and the stress condition under actual working environment, determine the hard phase region and soft phase region of speed reducer gear;Configuration laser heat treatment processing head, so that it can output a strip-shaped composite spot and cover the hardening area completely;Start laser quenching process, and combine with paraxial pyrometer to monitor and control the laser surface irradiation temperature in real time, control the strip-shaped composite spot from one end of the tooth to the other end along the tooth width direction, until the scanning of all tooth surfaces of speed reducer gear is completed.The application can obtain a laser quenching hardened layer combining soft phase and hard phase, solve the problem that the surface hardened zone is all martensite structure in the traditional laser quenching process, and improve the wear resistance and fatigue life of the gear for speed reducer.

Description

Technical Field

[0001] This invention belongs to the field of speed reducers, and specifically relates to a method for constructing a two-phase heterogeneous structure of speed reducer gears based on bar-shaped composite spot modulation scanning. Background Technology

[0002] As the core transmission component of a speed reducer, gears must possess a high-hardness surface and a strong, tough core. Therefore, gears for speed reducers made from low-carbon alloy steel, medium-carbon alloy steel, and ductile iron often require carburizing or nitriding heat treatment during actual production. However, chemical heat treatments such as nitriding require 5-7 days, resulting in a long production cycle and often leading to problems such as a thin hardened layer, low surface hardness, and unstable product quality. Therefore, speed reducer manufacturers urgently hope to replace traditional carburizing / nitriding with laser hardening technology for gear surface hardening, thereby shortening the production cycle, improving product quality, reducing production costs, and promoting high-quality development for enterprises.

[0003] Patent application number 202011400095.8 proposes a method and apparatus for laser hardening of gears to obtain a continuous and uniform hardened layer. It employs a scanning speed variation mode or a laser power density variation mode to perform laser scanning on all positions on the tooth surface, ultimately obtaining a uniform and continuous laser hardened layer. Patent application number 201910110698.5 proposes a composite surface treatment method for strengthening gear surfaces. This involves first performing laser hardening on the entire tooth surface of the gear, followed by two shot peening treatments on the laser-hardened tooth surface to obtain a gear with an overall hardened tooth surface. Patent application number 201810352252.9 proposes a method for avoiding tempering zones in laser surface hardening based on gear generating methods. This involves the laser beam moving along the involute trajectory of the gear, ensuring that the laser beam remains perpendicular to the gear tooth surface during tooth root processing, and scanning each tooth surface at a speed V to continuously complete the laser hardening treatment of the entire gear tooth surface. It can be seen that the above patents all use a laser beam to completely cover the entire tooth surface when performing laser quenching, that is, a hardened layer of a certain depth is formed at each position on the tooth surface. Summary of the Invention

[0004] This invention provides a method for constructing a two-phase heterogeneous structure for reducer gears. This method is based on obtaining strip-shaped composite light spots with adjustable intervals and controllable sizes using a segmented microlens array. By continuously moving the strip-shaped composite light spots on the tooth surface, a laser-hardened layer combining soft and hard phases is obtained. This solves the problem that the surface hardened area is entirely martensitic in the traditional laser hardening process, thereby improving the wear resistance and fatigue life of reducer gears.

[0005] The technical solution of this invention is as follows:

[0006] A method for constructing a two-phase heterogeneous structure for a speed reducer gear includes the following steps:

[0007] (1) Determine the hard phase region and soft phase region of the gear reducer based on the size and specifications of the gear reducer and the stress conditions under actual working environment; among them, the hard phase region is the region with high stress, namely the tooth tip region, the pitch circle meshing region and the tooth root region, and the remaining areas of the tooth surface are the soft phase region.

[0008] (2) Configure a laser heat treatment processing head so that it can output a strip-shaped composite light spot. The strip-shaped composite light spot includes a central strip unit and two edge strip units located on both sides of it. The distance between the two edge strip units and the central strip unit is equal, and the length of the central strip unit is greater than the length of the edge strip units.

[0009] (3) Adjust the size of the strip composite light spot so that the total length of the strip composite light spot is greater than the full tooth height of the reducer gear, and the length of the central strip unit can completely cover the pitch circle meshing area;

[0010] (4) Install and adjust the position of the laser heat treatment head so that the output strip composite spot is focused on any tooth surface, the width direction is consistent with the tooth width direction, the length direction is perpendicular to the tooth width direction, and the central strip unit of the strip composite spot can completely cover the pitch circle meshing area in the length direction.

[0011] (5) Use a pyrometer set on the off-axis to monitor the laser surface irradiation temperature at no less than one location within the strip composite spot irradiation area in real time, and adjust the laser power and scanning rate based on the real-time temperature data to form a closed-loop temperature control of the laser quenching temperature field.

[0012] (6) Start the laser quenching process and control the strip composite spot to scan from one end of the tooth to the other end along the tooth width direction, thus completing one laser scan of the tooth surface;

[0013] (7) Repeat step (6) until all tooth surfaces of the reducer gear are scanned.

[0014] Preferably, in step (1), a CCD industrial intelligent camera is used to reconstruct the three-dimensional profile of the gear, obtain the tooth thickness, tooth width, tooth profile and tooth height, and carry out stress simulation analysis to determine that the tooth tip region, pitch circle meshing region and tooth root region are hard phase regions, and the remaining areas of the tooth surface are soft phase regions.

[0015] Preferably, in step (2), the length of the strip composite spot varies from 10 to 40 mm, the width varies from 0.3 to 1 mm, the spacing between the strip units varies from 0.1 to 4 mm, the length of the central strip unit varies from 6 to 20 mm, and the length of the edge strip unit varies from 1.8 to 6 mm.

[0016] Preferably, in step (5), when laser quenching is performed, if the surface temperature of the irradiated area is below 850°C, the laser power is increased or the scanning speed is decreased; if the surface temperature of the irradiated area is above 1100°C, the laser power is decreased or the scanning speed is increased.

[0017] Preferably, in step (7), the number of laser scans for each tooth surface is 1 to 30. If the depth of the hardened layer is 0.3 to 0.5 mm, 1 to 3 laser scans are performed; if the depth of the hardened layer reaches 1.5 to 2 mm, 25 to 30 laser scans are performed.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The gear teeth of a reducer are subjected to uneven stress during service. This invention utilizes a strip-shaped composite laser spot to irradiate local areas of the gear teeth, thereby achieving hardening of the local areas through martensitic phase transformation. The non-laser-irradiated areas will not undergo phase transformation, which is the soft phase region. Finally, a surface structure combining soft and hard phases is obtained. This dual-phase heterogeneous structure can effectively prevent tooth root fracture. Compared with gears without surface strengthening treatment, the wear loss of gears with dual-phase heterogeneous structures can be reduced by 71.3%~85.2%, significantly improving the wear resistance of gears. Combining the stress analysis under the service conditions of gears with the optimization of the irradiation area and area of ​​the strip-shaped composite laser spot, this invention can increase the fatigue life of gears by 51.7%~86.1%.

[0020] (2) By adjusting the spacing between the microlens arrays and the distance between the conical parallel mirror and the focal plane, this invention can obtain strip-shaped composite light spots with adjustable spacing and controllable size. On the one hand, based on the service performance requirements such as the strength and toughness of gears, the content and distribution of soft and hard phases can be precisely controlled by changing the irradiation area ratio of the strip-shaped composite light spot, thereby obtaining gears with different performance. On the other hand, the overall size of the strip-shaped composite light spot is adjustable, which can meet the laser quenching treatment requirements of gears of various specifications. Attached Figure Description

[0021] Figure 1 A schematic diagram of the laser thermal treatment process using strip-shaped composite spot modulation scanning;

[0022] Figure 2This is a schematic diagram of a strip-shaped composite light spot. Detailed Implementation

[0023] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0024] like Figure 1 As shown, the present invention provides a laser heat treatment processing head with strip-shaped composite spot modulation scanning, including a collimating lens 1, a microlens array, a conical parallel mirror 8, a CCD camera 9, a beam combiner 10, and a pyrometer 11. The collimating lens 1, the microlens array, the conical parallel mirror 8, and the beam combiner 10 are coaxially arranged.

[0025] The microlens array includes, from top to bottom, a first microlens 2, a second microlens 3, a length focusing lens 4, a third microlens 5, a fourth microlens 6, and a width focusing lens 7. The first microlens 2, second microlens 3, and length focusing lens 4 are used to adjust the size of the light spot along its length; the third microlens 5, fourth microlens 6, and width focusing lens 7 are used to adjust the size of the light spot along its width. A conical parallel mirror 8 is used to form a strip-shaped composite light spot and to adjust the spacing and size of the stripe units within the composite light spot.

[0026] The laser beam is collimated into a parallel beam by collimating lens 1. The parallel beam is then homogenized and shaped in the length direction by the first microlens 2, the second microlens 3 and the length focusing lens 4. The beam is then homogenized and shaped in the width direction by the third microlens 5, the fourth microlens 6 and the width focusing lens 7. The beam is then divided into a strip composite beam composed of three strip unit beams by a conical parallel mirror 8. Finally, the beam is focused onto the processing surface by the beam combiner 10.

[0027] Both the CCD camera 9 and the pyrometer 11 are located on the side of the laser optical path. The CCD camera 9 is used to reconstruct the tooth profile in three dimensions, and the pyrometer 11 is used to monitor the laser irradiation temperature of the processed surface in real time.

[0028] Based on the aforementioned laser heat treatment head, this invention provides a method for constructing a two-phase heterogeneous structure for a reducer gear, comprising the following steps:

[0029] (1) Determine the hard phase region and soft phase region of the gear reducer based on the size and specifications of the gear reducer and the stress conditions under actual working environment. The hard phase region is the region with high stress, namely the tooth tip region, the pitch circle meshing region and the tooth root region, while the remaining areas of the tooth surface are the soft phase regions.

[0030] Preferably, a CCD industrial intelligent camera can be used to reconstruct the three-dimensional profile of the gear, obtain information such as tooth thickness, tooth width, tooth profile, and tooth height, and carry out stress simulation analysis to determine that the tooth tip region, pitch circle meshing region, and tooth root region are hard phase regions (i.e., laser hardened regions), while the remaining areas of the tooth surface are soft phase regions.

[0031] (2) Configure a laser heat treatment head so that it can output a linear composite light spot, such as Figure 2 As shown, the strip-shaped composite light spot includes a central strip unit 20 and two edge strip units 21 located on both sides thereon. The distance between the two edge strip units 21 and the central strip unit 20 is equal, and the length of the central strip unit 20 is greater than the length of the edge strip units 21.

[0032] Preferably, the length of the strip composite spot varies from 10 to 40 mm in the AC direction, the width varies from 0.3 to 1 mm in the AB direction, the spacing between the strip units 22 varies from 0.1 to 4 mm, the length of the central strip unit 20 varies from 6 to 20 mm, and the length of the edge strip unit 21 varies from 1.8 to 6 mm.

[0033] (3) Adjust the size of the strip composite spot, that is, by adjusting the spacing between each lens in the microlens array and the distance between the conical parallel mirror 8 and the beam combiner 10, an adjustable and controllable strip composite spot is obtained, so that the total length of the strip composite spot is greater than the full tooth height of the reducer gear, and the length of the central strip unit can completely cover the pitch circle meshing area.

[0034] (4) Install and adjust the position of the laser heat treatment head so that the output strip composite spot is focused on a tooth surface, and its width direction is consistent with the tooth width direction, and its length direction is perpendicular to the tooth width direction. The strip composite spot is required to completely cover the tooth root and tooth tip in the length direction, and the length of the central strip unit can completely cover the pitch circle meshing area.

[0035] (5) The laser surface irradiation temperature at at least one location within the strip-shaped composite spot irradiation area is monitored in real time using a pyrometer 11 mounted on a paraxial axis. Based on this real-time temperature data, the laser power and scanning rate are adjusted to form a closed-loop temperature control system for the laser quenching temperature field, thereby achieving controllable surface heating temperature of the laser irradiation area on the tooth surface. That is, during laser quenching, when the surface temperature of the irradiation area is below 850℃, the laser power is increased or the scanning speed is decreased; when the surface temperature of the irradiation area is above 1100℃, the laser power is decreased or the scanning speed is increased.

[0036] (6) Start the laser hardening process, so that the strip-shaped composite laser spot scans from one end of the tooth to the other along the tooth width direction, thus completing one laser scan of the tooth surface. Multiple scans can be repeated according to different hardening layer depth requirements. Preferably, the number of laser scans can be 1 to 30. If the required hardening layer depth is low (hardening layer depth is 0.3 to 0.5 mm), the tooth surface only needs to be scanned 1 to 3 times; if the required hardening layer depth reaches 1.5 to 2 mm, then 25 to 30 laser scans are required.

[0037] (7) After completing the laser scan of one tooth surface, rotate the gear by a certain angle and repeat step (6) to scan the next tooth surface until all tooth surfaces of the reducer gear are scanned. Example

[0038] (1) A standard spur gear with a module of 5 and 20CrMnTi steel was selected. The profile of the gear was reconstructed in three dimensions using a CCD camera to obtain information on the total height of the tooth, the tooth thickness, and the pitch circle diameter.

[0039] (2) Based on the gear parameter information, by adjusting the spacing between the microlenses in the two directions of the light spot length and width, and the distance between the conical parallel mirror and the focal plane, the composite strip light spot is obtained with a length of 10 mm, a width of 0.3 mm, a central strip unit length of 6 mm, an edge strip unit length of 1.8 mm, and a strip unit spacing of 0.1 mm.

[0040] (3) The laser head is mounted on a six-axis robot. The six-axis robot plans the scanning path so that the composite stripe spot completely covers the tooth root to tooth tip. The scanning is performed from one end of the tooth to the other end, and one scan is completed to complete the scanning of one tooth. After the scanning of one tooth is completed, the gear is rotated by a certain angle to scan the next tooth, until the quenching of all tooth surfaces is completed;

[0041] (4) For a certain area of ​​the surface to be irradiated, when the surface temperature of the laser irradiated area is higher than 950℃, reduce the laser power or increase the scanning speed; when the surface temperature of the laser irradiated area is lower than 850℃, increase the laser power or reduce the scanning speed to ensure that the surface temperature of the irradiated area is between 850℃ and 950℃ during laser irradiation.

[0042] This embodiment utilizes a microlens array and a conical parallel mirror to achieve simultaneous laser heat treatment of the gear's tooth tip, pitch circle meshing area, and tooth root, obtaining a laser-quenched tooth surface with a reinforced layer depth of 0.3 mm. Example

[0043] (1) A standard spur gear with a module of 8 and 20CrMnTi steel was selected. The profile of the gear was reconstructed in three dimensions using a CCD camera to obtain information on the total height of the tooth, the tooth thickness, and the pitch circle diameter.

[0044] (2) Based on the gear parameter information, by adjusting the spacing between the microlenses in the two directions of the light spot length and width, and the distance between the conical parallel mirror and the focal plane, the composite strip light spot is obtained with a length of 18mm, a width of 0.5mm, a central strip unit length of 9mm, an edge strip unit length of 3mm, and a strip unit interval of 1mm.

[0045] (3) The laser head is mounted on a six-axis robot. The six-axis robot plans the scanning path so that the composite stripe spot completely covers the tooth root to tooth tip. The scanning is performed from one end of the tooth to the other end, and the scanning is completed 3 times. After the scanning of one tooth is completed, the gear is rotated by a certain angle to scan the next tooth, until the quenching of all tooth surfaces is completed;

[0046] (4) For a certain area of ​​the surface to be irradiated, when the surface temperature of the laser irradiated area is higher than 950℃, reduce the laser power or increase the scanning speed; when the surface temperature of the laser irradiated area is lower than 900℃, increase the laser power or reduce the scanning speed to ensure that the surface temperature of the irradiated area is between 900℃ and 950℃ during laser irradiation.

[0047] This embodiment utilizes a microlens array and a conical parallel mirror to achieve simultaneous laser heat treatment of the gear's tooth tip, pitch circle meshing area, and tooth root, obtaining a laser-quenched tooth surface with a reinforced layer depth of 0.5 mm. Example

[0048] (1) A standard spur gear with a module of 14 and 20CrMnTi steel was selected. The profile of the gear was reconstructed in three dimensions using a CCD camera to obtain information on the total tooth height, tooth thickness and pitch circle diameter.

[0049] (2) Based on the gear parameter information, by adjusting the spacing between the microlenses in the two directions of the light spot length and width, and the distance between the conical parallel mirror and the focal plane, the composite strip light spot is obtained with a length of 32mm, a width of 0.7mm, a central strip unit length of 16mm, an edge strip unit length of 5mm, and a strip unit spacing of 3mm.

[0050] (3) The laser head is mounted on a six-axis robot. The six-axis robot plans the scanning path so that the composite stripe spot completely covers the tooth root to tooth tip. The scanning is performed from one end of the tooth to the other end, and the scanning is completed 25 times. After the scanning of one tooth is completed, the gear is rotated by a certain angle to scan the next tooth, until the quenching of all tooth surfaces is completed.

[0051] (4) For a certain area of ​​the surface to be irradiated, when the surface temperature of the laser irradiated area is higher than 1000℃, reduce the laser power or increase the scanning speed; when the surface temperature of the laser irradiated area is lower than 970℃, increase the laser power or reduce the scanning speed to ensure that the surface temperature of the irradiated area is between 970℃ and 1000℃ during laser irradiation.

[0052] This embodiment utilizes a microlens array and a conical parallel mirror to achieve simultaneous laser heat treatment of the gear's tooth tip, pitch circle meshing area, and tooth root, obtaining a laser-quenched tooth surface with a reinforced layer depth of 1.5 mm. Example

[0053] (1) A standard spur gear with a module of 18 and 20CrMnTi steel was selected. The profile of the gear was reconstructed in three dimensions using a CCD camera to obtain information on the total tooth height, tooth thickness and pitch circle diameter.

[0054] (2) Based on the gear parameter information, by adjusting the spacing between the microlenses in the two directions of the light spot length and width, and the distance between the conical parallel mirror and the focal plane, the composite strip light spot is obtained with a length of 40mm, a width of 1mm, a central strip unit length of 20mm, an edge strip unit length of 6mm, and a strip unit interval of 4mm.

[0055] (3) The laser head is mounted on a six-axis robot. The six-axis robot plans the scanning path so that the composite stripe spot completely covers the tooth root to tooth tip. The scanning is performed from one end of the tooth to the other end, and the scanning is completed 30 times. After the scanning of one tooth is completed, the gear is rotated by a certain angle to scan the next tooth, until the quenching of all tooth surfaces is completed;

[0056] (4) For a certain area of ​​the surface to be irradiated, when the surface temperature of the laser irradiated area is higher than 1100℃, reduce the laser power or increase the scanning speed; when the surface temperature of the laser irradiated area is lower than 980℃, increase the laser power or reduce the scanning speed to ensure that the surface temperature of the irradiated area is between 980℃ and 1100℃ during laser irradiation.

[0057] This embodiment utilizes a microlens array and a conical parallel mirror to achieve simultaneous laser heat treatment of the gear's tooth tip, pitch circle meshing area, and tooth root, obtaining a laser-quenched tooth surface with a reinforced layer depth of 2mm.

[0058] In addition to the embodiments described above, the present invention may have other implementations. All technical solutions formed by equivalent substitution or equivalent transformation fall within the protection scope claimed by the present invention.

Claims

1. A method for constructing a two-phase heterogeneous structure for a speed reducer gear, characterized in that, Includes the following steps: (1) Determine the hard phase region and soft phase region of the gear reducer based on the size and specifications of the gear reducer and the stress conditions under actual working environment; among them, the hard phase region is the region with high stress, namely the tooth tip region, the pitch circle meshing region and the tooth root region, and the remaining areas of the tooth surface are the soft phase region. (2) Configure a laser heat treatment processing head so that it can output a strip-shaped composite light spot. The strip-shaped composite light spot includes a central strip unit and two edge strip units located on both sides of it. The distance between the two edge strip units and the central strip unit is equal, and the length of the central strip unit is greater than the length of the edge strip units. (3) Adjust the size of the strip composite light spot so that the total length of the strip composite light spot is greater than the full tooth height of the reducer gear, and the length of the central strip unit can completely cover the pitch circle meshing area; (4) Install and adjust the position of the laser heat treatment head so that the output strip composite spot is focused on any tooth surface, the width direction is consistent with the tooth width direction, the length direction is perpendicular to the tooth width direction, and the central strip unit of the strip composite spot can completely cover the pitch circle meshing area in the length direction. (5) Use a pyrometer set on the off-axis to monitor the laser surface irradiation temperature at no less than one location within the strip composite spot irradiation area in real time, and adjust the laser power and scanning rate based on the real-time temperature data to form a closed-loop temperature control of the laser quenching temperature field. (6) Start the laser quenching process and control the strip composite spot to scan from one end of the tooth to the other end along the tooth width direction, thus completing one laser scan of the tooth surface; (7) Repeat step (6) until all tooth surfaces of the reducer gear are scanned.

2. The method for constructing a two-phase heterogeneous structure of a reducer gear according to claim 1, characterized in that, In step (1), a CCD industrial intelligent camera is used to reconstruct the three-dimensional profile of the gear, obtain the tooth thickness, tooth width, tooth profile and tooth height, and carry out stress simulation analysis to determine that the tooth tip region, pitch circle meshing region and tooth root region are hard phase regions, and the remaining areas of the tooth surface are soft phase regions.

3. The method for constructing a two-phase heterogeneous structure of a reducer gear according to claim 1, characterized in that, In step (2), the length of the strip composite spot varies from 10 to 40 mm, the width varies from 0.3 to 1 mm, the spacing between the strip units varies from 0.1 to 4 mm, the length of the central strip unit varies from 6 to 20 mm, and the length of the edge strip unit varies from 1.8 to 6 mm.

4. The method for constructing a two-phase heterogeneous structure of a reducer gear according to claim 1, characterized in that, In step (5), when laser quenching is performed, if the surface temperature of the irradiated area is below 850°C, the laser power is increased or the scanning speed is decreased; if the surface temperature of the irradiated area is above 1100°C, the laser power is decreased or the scanning speed is increased.

5. The method for constructing a two-phase heterogeneous structure of a reducer gear according to claim 1, characterized in that, In step (7), for each tooth surface, the number of laser scans is 1 to 30. If the hardened layer depth is 0.3 to 0.5 mm, 1 to 3 laser scans are performed; if the hardened layer depth reaches 1.5 to 2 mm, 25 to 30 laser scans are performed.

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